System and method for clean energy planned microgrid seamless transitions

Abstract

A method and system for transitioning between grid-tied and islanded modes of operation are disclosed. A plant may include a microgrid that includes one or more customer loads and that may provide power to a utility grid. The plant may include clean energy sources, such as DC-coupled photovoltaics and battery systems, as well as other types of clean energy generation and storage technologies. In certain instances, the plant may transition from grid-tied (in which the plant receives or provides power to the utility grid) to islanded (where the plant is disconnected from and does not receive or provide power to the utility grid), and vice-versa. The method and system may automatically transition between grid-tied and islanded without interruption of power to the one or more customer loads.

What is claimed is: 
     
         1 . A method for transitioning a plant between grid-tied and islanded, wherein the plant includes at least one microgrid supplying power to one or more customer loads, wherein the plant when grid-tied is providing to or receiving power from at least a part of a grid that is operated by a utility, wherein the plant when islanded is disconnected from providing or receiving power to the at least a part of the grid, the method comprising:
 responsive to an indication to transition the plant between grid-tied and islanded:
 performing one or more checks prior to the transition, the one or more checks comprising:
 for the transition from grid-tied to islanded: determining an amount of power provided to the grid and an amount of power provided to the one or more customers of the plant; or 
 for the transition from islanded to grid-tied: determining, by the plant, whether sensed frequency, sensed voltage and sensed phase angle on both sides of the at least one islanding breaker is within a predetermined tolerance; 
 
 responsive to performing the one or more checks prior to the transition, determining whether to perform one or more actions, the one or more actions comprising:
 for the transition from grid-tied to islanded: responsive to determining the amount of power provided to the grid and the amount of power provided to the one or more customers of the plant, modifying power output of the plant to be the amount of power provided to the one or more customers loads of the at least one microgrid; or 
 for the transition from islanded to grid-tied: responsive to determining by the plant that the sensed frequency, the sensed voltage, and the sensed phase angle on both sides of the at least one islanding breaker are not within the predetermined tolerance, performing at least one action so that the sensed frequency, the sensed voltage, and the sensed phase angle on both sides of the at least one islanding breaker are within the predetermined tolerance; and 
 
 after determining whether to perform the one or more actions and performing the one or more actions, causing the at least one islanding breaker to change its state thereby transitioning the plant between grid-tied and islanded. 
   
     
     
         2 . The method of  claim 1 , wherein the transition is from grid-tied to islanded; and
 wherein responsive to receiving the indication to transition the plant from grid-tied to islanded:
 the amount of power provided to the grid and the amount of power provided to the one or more customers of the plant is determined; 
 the power output of the plant is modified to be the amount of power provided to the one or more customers loads of the at least one microgrid; and 
 after modifying the power output of the plant to be the amount of power provided to the one or more customers loads of the at least one microgrid, the at least one islanding breaker is caused to be opened, thereby islanding the plant from the grid. 
   
     
     
         3 . The method of  claim 2 , wherein modifying the power output of the plant to be the amount of power provided to the one or more customers loads of the at least one microgrid comprises modifying the power output to be within a predetermined tolerance of the amount of power provided to the one or more customers loads of the at least one microgrid. 
     
     
         4 . The method of  claim 2 , wherein causing the at least one islanding breaker to open comprises the plant notifying the utility that the at least one islanding breaker is to be opened so that the utility commands the at least one islanding breaker to open. 
     
     
         5 . The method of  claim 4 , wherein the plant notifying the utility that the at least one islanding breaker is to be opened further causes the utility to perform one or more additional checks prior to commanding the at least one islanding breaker to open. 
     
     
         6 . The method of  claim 5 , wherein the one or more additional checks comprises verifying frequency and voltage are within the predetermined tolerance. 
     
     
         7 . The method of  claim 2 , wherein the indication to transition the plant from grid-tied to islanded is received from the utility; and
 wherein responsive to the plant receiving from the utility the indication to transition the plant from grid-tied to islanded, the plant: determines the amount of power provided to the grid and the amount of power provided to the one or more customers of the at least one microgrid; modifies the power output of the plant to be the amount of power provided to the one or more customers loads of the at least one microgrid; and causes the at least one islanding breaker to open, thereby islanding the plant from the grid.   
     
     
         8 . The method of  claim 2 , wherein the indication to transition the plant from grid-tied to islanded is generated by the plant. 
     
     
         9 . The method of  claim 2 , wherein causing the at least one islanding breaker to change its state thereby transitioning the plant from grid-tied to islanded comprises sending a communication from the plant to the utility indicating ready to island. 
     
     
         10 . The method of  claim 9 , wherein the communication from the plant to the utility indicating ready to island is indicative to the utility to perform additional checks prior to the utility controlling at least one islanding breaker to transition the plant from grid-tied to islanded. 
     
     
         11 . The method of  claim 10 , wherein the plant has performed verification that the sensed frequency and the sensed voltage on both sides of the at least one islanding breaker is within the predetermined tolerance prior to sending the communication from the plant to the utility indicating ready to island; and
 wherein the communication from the plant to the utility indicating ready to island is indicative to the utility for the utility to verify that the sensed frequency and the sensed voltage on both sides of the at least one islanding breaker is within the predetermined tolerance.   
     
     
         12 . The method of  claim 1 , wherein the transition is from islanded to grid-tied; and
 wherein responsive to the indication to transition the plant from islanded to grid-tied:
 determining, by the plant, whether the sensed frequency, the sensed voltage and the sensed phase angle on both sides of the at least one islanding breaker is within the predetermined tolerance; 
 responsive to determining by the plant that the sensed frequency, the sensed voltage, and the sensed phase angle on both sides of the at least one islanding breaker are not within the predetermined tolerance, performing the at least one action so that the sensed frequency, the sensed voltage, and the sensed phase angle on both sides of the at least one islanding breaker are within the predetermined tolerance; and 
 responsive to the plant determining that the sensed frequency, the sensed voltage, and the sensed phase angle on both sides of the at least one islanding breaker is within the predetermined tolerance: 
 performing at least one of:
 commanding the at least one islanding breaker to transition from islanded to grid-tied only after receiving from the utility confirmation that the utility determined that the sensed frequency, the sensed voltage, and the sensed phase angle on both sides of the at least one islanding breaker is within the predetermined tolerance; or 
 notifying the utility that the sensed frequency, the sensed voltage, and the sensed phase angle on both sides of the at least one islanding breaker is within the predetermined tolerance in order to cause the utility to command the at least one islanding breaker to transition from islanded to grid-tied only after receiving from the utility confirmation that the utility determined that the sensed frequency, the sensed voltage, and the sensed phase angle on both sides of the at least one islanding breaker is within the predetermined tolerance. 
 
   
     
     
         13 . The method of  claim 12 , wherein the plant, via at least two separate devices, determines whether the sensed frequency and the sensed voltage on both sides of the at least one islanding breaker is within the predetermined tolerance. 
     
     
         14 . The method of  claim 13 , wherein the plant includes a plant real-time automation controller (RTAC) and a plant power plant controller (PPC); and
 wherein both the plant RTAC and a plant PPC separately determine whether the sensed frequency and the sensed voltage on both sides of the at least one islanding breaker is within the predetermined tolerance.   
     
     
         15 . The method of  claim 12 , wherein the at least one action comprises modifying at least one of the sensed frequency, the sensed voltage or the sensed phase angle of the plant. 
     
     
         16 . The method of  claim 12 , wherein the at least one action comprises waiting at least a predetermined amount of time so that the sensed frequency, the sensed voltage, and the sensed phase angle on both sides of the at least one islanding breaker are within the predetermined tolerance. 
     
     
         17 . The method of  claim 1 , wherein the transition is from grid-tied to islanded; and
 wherein the transition is seamless in that there is no interruption in power to the one or more customer loads.   
     
     
         18 . The method of  claim 1 , wherein the transition is from islanded to grid-tied; and
 wherein the transition is seamless in that there is no interruption in power to the one or more customer loads.   
     
     
         19 . A plant configured to supply power to one or more customer loads and to supply the power to or receive the power from a grid that is operated by a utility, the plant comprising:
 at least one microgrid configured to supply the power to the one or more customer loads;   communication functionality configured to communicate with the utility; and   at least one controller configured to:
 control the power supplied by the at least one microgrid to the one or more customer loads; 
 responsive to an indication to transition the plant between grid-tied and islanded:
 perform one or more checks prior to the transition, the one or more checks comprising:
 for the transition from grid-tied to islanded: determining an amount of power provided to the grid and an amount of power provided to the one or more customers of the plant; or 
 for the transition from islanded to grid-tied: determining, by the plant, whether sensed frequency, sensed voltage and sensed phase angle on both sides of the at least one islanding breaker is within a predetermined tolerance; 
 
 responsive to performing the one or more checks prior to the transition, determine whether to perform one or more actions, the one or more actions comprising:
 for the transition from grid-tied to islanded: responsive to determining the amount of power provided to the grid and the amount of power provided to the one or more customers of the plant, modifying power output of the plant to be the amount of power provided to the one or more customers loads of the at least one microgrid; or 
 for the transition from islanded to grid-tied: responsive to determining by the plant that the sensed frequency, the sensed voltage, and the sensed phase angle on both sides of the at least one islanding breaker are not within the predetermined tolerance, performing at least one action so that the sensed frequency, the sensed voltage, and the sensed phase angle on both sides of the at least one islanding breaker are within the predetermined tolerance; and 
 
 after determining whether to perform the one or more actions and perform the one or more actions, cause the at least one islanding breaker to change its state thereby transitioning the plant between grid-tied and islanded. 
 
   
     
     
         20 . The plant of  claim 19 , wherein the at least one controller is configured to cause the at least one islanding breaker to change its state thereby transitioning the plant from grid-tied to islanded by sending a communication from the plant to the utility indicating ready to island. 
     
     
         21 . The plant of  claim 20 , wherein the communication from the plant to the utility indicating ready to island is indicative to the utility to perform additional checks prior to the utility controlling at least one islanding breaker to transition the plant from grid-tied to islanded. 
     
     
         22 . The plant of  claim 21 , wherein the at least one controller is configured to perform verification that the sensed frequency and the sensed voltage on both sides of the at least one islanding breaker is within the predetermined tolerance prior to sending the communication from the plant to the utility indicating ready to island; and
 wherein the communication from the plant to the utility indicating ready to island is indicative to the utility for the utility to verify that the sensed frequency and the sensed voltage on both sides of the at least one islanding breaker is within the predetermined tolerance.